Can 'clean diesel' power past gasoline?

To those worried about air pollution, America's enginemakers want to say two words: Clean diesel.

Admittedly, it sounds like a contradiction. Nevertheless, urged on by ever-tougher emissions standards, manufacturers and researchers are turning sooty old truck engines into clean-burning power plants.

If they meet the challenge, the nation's trucks, buses  even many of its sport-utility vehicles and cars  will be running on clean diesel for years to come.

The technology may raise the costs of driving. It will almost certainly boost the nation's freight bill. Still, it would push onto America's highways vehicles that get higher mileage and pollute less than today's cars and trucks.

"Not very many experts in this field have much faith in the future of gasoline engines," says Stephen Ciatti, a clean-diesel researcher at Argonne National Laboratory in Argonne, Ill. "Either diesel engines or fuel cells will be the likely contenders as the power plants for future transportation needs." (One environmental advocate bets on fuel cells, see story.)

Even some environmentalists acknowledge diesel has a role to play, at least in trucks and heavy equipment, if it can meet future clean-air requirements.

"Once those standards kick in, those big smoking diesel trucks we've all come to know and hate will be a thing of the past," says Frank O'Donnell, executive director of the Clean Air Trust, a Washington, D.C., environmental group.

Already, momentum is building. At last month's Paris Auto Show, 13 chief executives of the world's top automakers issued a joint statement calling for, among other things, a universal standard for and acceptance of clean-diesel technology. Diesel already powers 3 of every 10 new cars sold in Western Europe and, according to one forecast, may run half of them by 2006.

In the United States, domestic and foreign automakers are beginning to offer diesel-powered models again after a long lull. Volkswagen has built a small but fanatical following with diesel-powered Jettas, Golfs, and Beetles. Ford and General Motors now offer diesel-powered pickup trucks. And this time they promise to run cleaner and better than the models that appeared in the 1970s.

Of the five most fuel-efficient cars in the US today, the top two are hybrid-gasoline Japanese cars, followed by three diesel-powered Volkswagen models. The reason: Diesel engines remain inherently more efficient than gasoline-powered cars. And they produce less carbon dioxide, a greenhouse gas.

So when Volkswagen wanted to show off a high-mileage car of the future at its annual meeting last April, its outgoing chief executive drove a tiny diesel-powered prototype that got a whopping 285 miles to the gallon.

Of course, diesel engines have their drawbacks. They emit nitrogen oxides (NOx), which produce smog, and very fine airborne particles linked by some to thousands of premature deaths each year. By tightening emission and other standards, governments on both sides of the Atlantic have begun to push enginemakers to improve their technology.

In 2005, tough new clean-air standards will challenge European automakers to create even cleaner diesel engines. A year later, the US will require diesel fuel to meet low-sulphur requirements. Low-sulphur fuel should prove a key benefit for US automakers, allowing them to build less-polluting diesel pickups, vans, and sport-utility vehicles.

"We think there's an opportunity in the US," says Allen Schaeffer, executive director of the Diesel Technology Forum, a consortium of manufacturers based in Frederick, Md. "If you could get 40 miles per gallon in your SUV, a lot of people would be interested."

The tougher challenge lies in truck engines, which spew more pollution and where fuel economy is critical. For example, new federal emissions regulations that took effect Oct. 1. have slowed semi trailer-truck sales to a crawl. That's because, for the first time, diesel-engine manufacturers have failed to lower the cost of operation while meeting clean-air standards, notes Bob Costello, chief economist with the American Trucking Associations (ATA) in Alexandria, Va.

Instead, they're using technology that boosts the cost of a new truck by some $5,000 to $8,000 and actually lowers fuel efficiency by 3 to 5 percent. Added maintenance on the new engines could cost truckers an extra $6,000 over the life of their vehicle, the ATA estimates.

No wonder truck salesrooms have cleared out in the past two weeks. Many fleet managers bought their trucks before Oct. 1 to avoid buying the more costly and less proven engines.

"Nobody knows what they're going to do," says Roger Weiler, new-truck sales manager for Kenworth of St. Louis, a truck dealership in suburban Fenton, Mo. But "eventually they're going to have to buy them.... I'd say in six months we'll see a pickup."

That prediction may prove too optimistic, says Tom Rhein, president of Rhein Associates, a diesel-engine and truck research company and newsletter publisher in Canton, Mich. He estimates new truck sales could fall to as low as 125,000 next year  half the total sales of year 2000.

If truckers are leery of the new technology  called cooled exhaust gas recirculation  they're not alone. Although it cuts enough NOx to pass the Oct. 1 standards, it does little to help manufacturers meet the much stricter 2007 specifications. Those standards call for a 90 percent reduction in the fine particles diesels spew out.

That's why Caterpillar, the nation's top seller of large, heavy-duty truck engines, is trying to leapfrog its competitors with its next-generation engine, which uses advanced-combustion emissions-reduction technology.

Using electronic controls, the engine burns more of the diesel fuel at the point of combustion than traditional engines do. That means fewer emissions at the tailpipe. So far, the company sounds optimistic that the process can help meet the 2007 standards cost-effectively.

"We believe that clean diesel is going to take us through the next decade for sure in terms of a primary power source," says Jim Parker, vice president of the power-systems marketing division for Caterpillar, in Peoria, Ill.

There's only one problem. The new technology isn't ready yet. Now being tested in undisclosed locations around the country, it won't appear in a production engine until sometime next quarter, and won't be fully rolled out until the end of next year.

Until then, the company will have to pay federal clean-air penalties of anywhere from $3,000 to $4,500 for every engine sold.

Caterpillar has promised not to pass on the cost to its consumers and claims the penalties  in this slow sales period  won't affect its bottom line significantly.

Still, in the larger context, the added expense of these various engine technologies undoubtedly will raise the nation's transportation costs. Already, trucks haul some 8.8 billion tons of goods every year, accounting for 86 percent of the nation's freight bill.

When the new 2007 rules kick in, trucking costs will rise, says Mr. Costello of the American Trucking Associations.

Whatever technology wins, it will only gradually clean up the air. Truck engines typically last about a decade  longer if they're rebuilt. Manufacturers and regulators are starting to look at how they might retrofit existing trucks with pollution controls.